The moon is the planet given to us by God to live on.
Despite what scientists might have us believe, it is the only
planet in our solar system that humanity can comfortably inhabit.
The moon is a paradise for the creatures that live on it.
Every species on the moon has its place in the circle of life.
Human beings need food, clothing, shelter to survive.
All of these are provided in ample supply on God’s green moon…
I would have been happy with the moon being called Endor (referred to as a sanctuary moon), and the planet (a gas giant, so you can’t live on it) called something else. But back when these things were being figured out, the dark times, non-canonical sources such as the folks writing the role playing game, West End Games, made some of these decisions somewhat arbitrarily, and they sadly still stick around.
If you squint and assume that, rather than proper names, the designations are part of a cataloguing system, it almost makes sense. Two suns, some uninhabitable planets and smaller bodies, and one inhabitable moon that’s referred to as a “Sanctuary Moon” (possibly indicating that it was placed off-limits to development by the Republic at some point to protect the native developing sapients). No one bothered to give the celestial bodies in the system names, they just numbered them.
Later, when the Empire started their little project in the system and people started needing to talk about the body where the Imperials had their base, they just used the system name for it, dropping the catalog number because there was only one body of interest in the system. “Forest moon” might be less a clarification of location than a quick summary of local conditions.
FWIW the original RotJ Novelization said the gas giant was called Endor and the location of the shield generator and Ewoks (a word incidentally never said once in the movie) was a moon of Endor.